Best Free Browser DevTools in 2026

Your AI-powered browser for focused deep work

4.3/5 across G2 and SourceForge · 16 ratings, Jun 2026

Dia is a specialized browser engineered to optimize professional workflows by intelligently organizing information and proactively suggesting relevant content. It acts as a central hub, integrating with various work tools like GSuite, Slack, Notion, and GitHub to provide a unified view of tasks and information. Dia aims to reduce context switching and information overload, allowing users to concentrate on deep work. The browser features include a "Morning Brief" for daily overviews, "Proactive Suggestions" that surface next steps, and an AI-powered search that answers questions by analyzing context across connected applications. It also offers features for better meeting preparation, distinct work and personal profiles, and advanced tab management. Dia prioritizes user privacy with local data storage, end-to-end encryption for synced data, and strict controls over data sharing for product improvement.

An agentic browser that answers questions and takes action across tabs

3.8/5 across PeerSpot and G2 · 15 ratings, Sep 2026

Comet is Perplexity's AI-powered web browser. It builds Perplexity's answer engine directly into the browser, letting you ask questions about any page, summarize articles, and use an AI assistant that can take actions across your tabs. It is positioned as an agentic browser that completes tasks, not just one that displays pages.

Build, test, and debug APIs faster with a lightweight, open-source API client and web debugger.

4.7/5 on G2 · 5 ratings, Oct 2026

Requestly is an open-source, lightweight API client and web proxy designed for modern developers to build, test, and debug APIs efficiently. It offers both a browser extension for instant, in-browser functionality and a more powerful desktop application for Mac (with other platforms implied) to handle web, mobile, and desktop app API interactions. Beyond just an API client, Requestly functions as a robust HTTP interceptor and web debugger. It allows developers to intercept and modify network requests, headers, and API responses in real-time. This includes injecting custom scripts (JavaScript/CSS), mocking API responses to build frontends without a backend, simulating edge cases, and redirecting requests. It aims to streamline development workflows by providing a comprehensive tool for API development, testing, and debugging, reducing the need to juggle multiple tools. Requestly also emphasizes collaboration and enterprise-readiness with features like team workspaces, Git synchronization for API collections, role-based access control, and robust security measures including SOC-II compliance, SSO, and data encryption. It positions itself as a powerful, open-source alternative to more 'bloated' closed-source solutions, offering a fast, flexible, and secure environment for API development and debugging.

Boost your website's SEO, speed, and security with comprehensive auditing.

Checkbot is a powerful Chrome extension designed to audit websites for over 50 best practices related to SEO, web speed, and security. It can crawl hundreds of pages in minutes, identifying issues such as broken links, duplicate content, invalid HTML, insecure forms, redirect chains, and more. The tool provides immediate feedback, allowing users to catch critical problems during development before they impact users or search rankings. This tool is ideal for web developers, SEO specialists, product managers, and anyone involved in website optimization. It helps save time on manual testing by effortlessly and reliably checking numerous pages, uncovering hard-to-spot problems that might otherwise be missed. Checkbot also offers in-app guidance to explain identified issues, why they are important, and how to fix them, making it accessible even for those new to website optimization. It supports testing of unlimited sites, including local development and password-protected pages, ensuring continuous website health.

Solve accessibility issues in web and Windows applications before they reach your customers.

Accessibility Insights is a set of open-source tools designed to help developers find and fix accessibility issues in both web and Windows applications. It offers a browser extension for Chrome and Microsoft Edge, and a desktop application for Windows, enabling comprehensive accessibility testing. The tools are built to integrate seamlessly into development workflows, providing quick checks like FastPass to identify common, high-impact issues within minutes, as well as more in-depth assessment capabilities. It's ideal for developers, QA testers, and anyone involved in building software who wants to ensure their products are inclusive and compliant with accessibility standards like WCAG 2.1 AA.

Core performance metrics by Google

Web Vitals measures user experience metrics. Core Web Vitals from Google-the metrics that matter for search and users. The metrics are Google's standard. The measurement is accurate. The optimization is guided. Sites wanting to improve user experience track Web Vitals for Google's key metrics.

AI agents control real browsers via token-efficient ASCII wireframes

Agent Browser enables AI agents to navigate, click, type, and interact with real web browsers using ASCII wireframes, a text-based representation where interactive elements are numbered for efficient token usage. Instead of processing heavy screenshots, AI models receive structured wireframes that maintain semantic clarity while minimizing cost and latency. Built on Playwright, it integrates with MCP clients (Claude Desktop, Cursor), the Vercel AI SDK, and offers an interactive CLI for manual testing.

Modify HTTP request and response headers directly from your browser for web development and debugging.

ModHeader is a popular browser extension designed to help web developers and QA engineers modify HTTP request and response headers. It allows users to easily add, modify, or remove headers such as authorization, set-cookie, and custom headers, directly within their browser. This functionality is crucial for tasks like simulating different user environments, testing API endpoints, debugging web applications, and verifying security policies. The extension streamlines the development workflow by enabling quick changes to header values without needing to alter server-side code or proxy configurations. It's particularly useful for testing various scenarios like different IP addresses, locales, CORS issues, and feature flags. By providing granular control over HTTP headers, ModHeader helps in faster debugging, reducing the time spent on identifying and fixing header-related issues, and ultimately minimizing production bugs. Beyond header modification, ModHeader also offers related tools like a header tester to inspect current request/response headers, and editors for Content-Security-Policy (CSP) and Permissions-Policy headers. These additional tools further empower developers to ensure web application security and functionality.

Offload third-party scripts to a web worker for improved main thread performance.

Partytown is a lightweight library designed to help websites achieve significant performance improvements by moving resource-intensive third-party scripts off the main thread. It accomplishes this by executing these scripts within a web worker, isolating their impact on the main thread and preventing them from blocking critical rendering paths. This approach is particularly beneficial for sites heavily reliant on analytics, advertising, or other third-party integrations that can often degrade user experience. Developers and performance-conscious website owners are the primary audience for Partytown. By implementing Partytown, they can ensure their core web vitals remain strong, leading to better SEO, higher conversion rates, and a smoother, more responsive user interface. It's an excellent solution for anyone looking to optimize their site's loading speed and overall performance without completely removing essential third-party functionalities.

The quickest way to fill all inputs on a page with fake data for testing forms.

Fake Filler is a popular browser extension designed to streamline the process of testing web forms by automatically populating all input fields with fake data. This tool is invaluable for developers, QA testers, and anyone who frequently interacts with forms during application development or testing phases. It eliminates the tedious and time-consuming task of manually entering data into lengthy forms, significantly boosting productivity. The extension offers robust customization options, allowing users to tailor its behavior to specific requirements, even though it comes with sensible defaults. It supports synchronization of settings across multiple browsers where the extension is installed, ensuring a consistent experience. Fake Filler works seamlessly across various web technologies, including React, Vue.js, and Angular, making it a versatile solution for modern web development workflows.

Inspect, replace, and test fonts live on any website

Tinkerfont is a browser extension (for Chrome and Firefox) that lets you inspect, replace, and test fonts on any live website. It is designed for designers, developers, and typography enthusiasts who want to see how a typeface performs across real content, layouts, and breakpoints without editing CSS or leaving the browser. The tool includes a right-click font inspector, a scanner to list every font in use on a page, and a swap feature that offers a large selection of fonts from Bunny Fonts or custom uploaded files. Changes can be scoped to specific areas of a page, and all rules persist per hostname in local storage, making it easy to iterate on staging or reference sites over multiple sessions. Tinkerfont does not require an account, collects no data, and is free to use with optional supporter contributions.

The AI-powered browser for focused work and enhanced productivity.

Sidekick Browser is a Chromium-based web browser designed to enhance productivity and streamline workflows, particularly for professionals and teams. It integrates various tools and features to minimize distractions and optimize task management. Key functionalities include a built-in session manager, application sidebar for quick access to web apps, and a unified search across all open tabs and applications. Sidekick aims to reduce tab clutter and context switching by centralizing frequently used applications and providing a dedicated workspace for different projects. It's particularly beneficial for users who juggle multiple web-based tools, communication platforms, and research tabs, offering a more organized and efficient browsing experience. The browser also incorporates AI features to assist with tasks like summarization and content generation, further boosting productivity.

Instantly reveal web page architecture, frameworks, and components

Archify is a free, open-source browser extension that helps developers quickly understand the architecture behind any web page. By simply hovering over elements, it reveals the frameworks, UI libraries, APIs, analytics, hosting, and security components that make up the application, all processed locally with nothing sent to external servers. Each detection includes a confidence score, and unknown elements are honestly reported as unknown. The tool addresses the growing challenge of understanding modern software, which is increasingly complex despite being easier to build. Developers spend a significant portion of their time comprehending code rather than writing it, especially in the browser. Archify surfaces the system behind the interface: components, network calls, form listeners, third-party scripts, payment processors, and more. It integrates seamlessly into the browser workflow, providing instant insights without switching to DevTools or reading documentation. Archify is built for frontend engineers tracing bugs, QA engineers needing technical context for reports, and technical founders analyzing competitor stacks. It detects 100+ fingerprints across frameworks (React, Next.js, Vue, Angular, etc.), UI libraries, analytics pixels, commerce platforms, CMS, hosting providers, and security defenses. Every reading is verifiable with evidence, and the tool never fabricates information.

Send screen nudges to friends across popular web apps to grab their attention.

WizzyPoke is a Chrome extension that allows users to send "nudges" to their friends, reminiscent of the classic MSN Messenger feature. These nudges shake the recipient's screen, aiming to get their attention when messages might go unnoticed. It's designed for personal use to add a fun and immediate way to communicate. The tool works across popular web applications like WhatsApp Web, YouTube, and Netflix. It prioritizes privacy by using unique 6-digit codes for pairing friends instead of phone numbers. WizzyPoke is ideal for individuals looking for a playful and effective way to get a friend's attention online, especially when text messages aren't cutting through the noise. Key benefits include instant delivery of nudges, easy friend pairing, and the ability to make communication more engaging. It offers a free tier for basic use and a one-time purchase for unlimited nudges and broader web app support.

Browser-based Android debugging tool for seamless development and testing.

ADB Wrench is a browser-based tool designed to simplify Android debugging. It allows developers to connect to Android devices directly from their web browser, eliminating the need for local ADB installations or complex command-line interfaces. This makes it easier to inspect device state, install/uninstall apps, pull/push files, and execute shell commands. The tool is ideal for Android developers, QA engineers, and anyone who needs to interact with Android devices for development, testing, or troubleshooting. Its browser-based nature enhances accessibility and collaboration, as it can be used from any machine with a web browser without environment setup. Key benefits include increased productivity, reduced setup time, and a more streamlined debugging workflow.